Public Switched Telephone Network
Attempting to understand how the telephone used to work. --DarrinEden
FXO - Foreign Exchange Office. An interface that connects to the Public Switched Telephone Network's (PSTN) central office and is the interface offered on a standard telephone. Example: RJ-11 connector that allows analog connection to the central office.
FXS - Foreign Exchange Subscriber. An interface that connects directly to a standard telephone and supplies ring, voltage, and dial tone. Example: RJ-11 connector allows connections to basic telephone equipment.